The present invention relates to self-cleaning plates which are applied in cooking appliances as cooking members such as the inner walls of the cooking appliance, and which at cooking temperature can automatically clean off dirt such as the fat and grease that spatters from food during cooking.
As to methods for automatically cleaning off the dirt that spatters onto the inner wall surfaces of cooking appliances when food is being cooked by a cooking appliance such as an oven, an oven toaster, or a microwave oven, there have been disclosed by, to begin with, U.S. Pat. No. 3,266,477, as well as U.S. Pat. Nos. 3,547,098, 3,580,733, 3,598,650, 3,671,278, and 3,759,240, and Japanese Patent Publication No. 17832/1972, and a number of others besides. The self-cleaning method which forms the mainstream of these disclosures is that of oxidative destruction of the dirt that is spattered from food at cooking temperature, by the action of an oxidation catalyst contained in a porous layer formed using a glass frit as a binder, that is to say, as a coating layer forming material, and forming a porous layer by coating and baking it on a base layer of enamel coated onto a metal substrate. By the action of this oxidation catalyst contained in the porous layer, the dirt spattered from the food during cooking is oxidatively destroyed. However, there are defects such that at high temperatures of 800.degree. C. or more, these calcine, and so the fusion and sintering of the particles of oxidation catalyst occur, reducing the cleaning performance, such that if the sheet is not of a certain thickness it may distort, it use a large amount of energy, a high temperature calcining furnace is needed and the catalyst layer cannot be made thick. To remedy these defects substances using an alkali silicate as the binder, such as, for instance, in Japanese Patent Publication No. 28120/1974, have been proposed. As a binder type, this belongs to the heat resistant coating group, and a calcining temperature of about 260.degree. C. to 316.degree. C. (500.degree. F. to 600.degree. F.) is sufficient, and so it could be said that it remedies the aforementioned defects. In the inventor's experiments it was also confirmed that inorganic coating agents of silicas, aluminas or phosphates can be used as binders with the aforementioned advantages and which are capable of forming a porous coating with heat resistant properties. However, the facts are that when a binder containing catalytic particles is coated onto a substrate metal (steel plate, stainless steel plate, aluminized steel plate, etc.) it has poor adhesion to the substrate, produces cracks due to heat shock and steam, etc., and peels off easily, and when it is used in a cooking appliance, a long life for the coating layer cannot be guaranteed.
The present invention, giving full consideration to the aforementioned circumstances presents a self-cleaning plate of high cleaning capability and which eliminates the defects present in the prior art.